A. Technical Field
The present invention relates to a method for the measurement and analysis of tyre air pressure with an allocation of wheel positions of a vehicle to be analysed in a system for tyre air pressure measurement, and a corresponding system for tyre air pressure measurement for carrying out the method.
B. Background of the Invention
Modern vehicles have tyre air pressure monitoring systems which determine the current tyre air pressure and warn the driver if a deviation occurs from a predetermined tyre air pressure. Tyre air pressure monitoring systems of this kind contribute considerably to the safety of vehicles.
Systems of generic kind are normally equipped with pressure sensors in the tyres, which transmit the current air pressure to a central analysis unit. In these, each wheel of the vehicle is allocated an air pressure checking device, which transfers the information to the analysis unit together with an individual wheel identifier. A problem with this arrangement, among other things, is that the data transfer must take place in a largely error-free manner. Furthermore, a particular problem consists in the fact that the air pressure checking device may be allocated to a specific wheel position. If this were not the case, the driver might not be informed about a problem at a specific wheel position. If the wheel is changed however and eventually mounted at a different position on the vehicle, then the allocation of the air pressure checking device of the corresponding wheel to a specific wheel position of the vehicle cannot be guaranteed. In order to eliminate this source of error, systems for the allocation of air pressure checking devices to specific wheel positions and wheel detection in them have been described in the prior art.
Thus for example EP 0 806 307 A2 discloses sensors, which simply measure the current rotation rate of the wheel using the energies generated by the wheel rotation, and transmit it to a receiver associated with them. Via a cable between the receiver and a central unit the current rotation rate of the respective wheel is transmitted to a central unit. A disadvantage of this arrangement is that there is a relatively high cost for the cabling of the receivers and a corresponding sensitivity to interference.
From EP 1 807 270 B1 a wheel detection system is known, which uses signals at radio frequencies and a received signal amplitude that varies periodically owing to the rotation of the wheel, to allow the current rotation rate of the wheel to be estimated. A disadvantage of this arrangement is that the radio-frequency is susceptible to interference, since reflections from the surroundings can cause interference and signal dropout effects to occur. This means it is difficult to determine a periodicity from the signals from which the rotation rate is derived.